What do HVAC Ratings Really Mean?

When you’re choosing a new HVAC system for your home, one of the most important factors to consider is efficiency. Every HVAC unit is labeled with a rating of some kind that tells you how efficient it is. Here are three of the most common ratings used and what they mean.

1. SEER (Seasonal Energy Efficiency Ratio):

The SEER rating is used to measure the efficiency of air conditioners. According to the US Department of Energy, the SEER rating is determined by measuring the total amount of heat removed during the entire cooling season, then dividing that amount by the total amount of energy used. The benefit of this rating method is that it determines the average efficiency of the air conditioning unit over the wide range of conditions that you may get over the course of the warm months of the year.

At present, all new air conditioners sold in the US must have at least a SEER rating of 14, while air conditioners with a SEER rating of 15 or more are generally considered high-efficiency.

2. HSPF (Heating Seasonal Performance Factor):

The HSPF rating is very similar to the SEER rating, except that HSPF measures the efficiency of a heat pump instead of an air conditioner. Of course, since heat pumps also act as air conditioners, depending on which mode they’re in, a heat pump will generally have both an HSPF rating and a SEER rating. The Department of Energy explains that, like the SEER rating, the HSPF is determined by measuring the total amount of heat produced across the entire heating season, then dividing that amount by the total amount of energy used.

Currently, new heat pumps sold in the US must have a minimum HSPF rating of 8.2, while those with an HSPF of 8.5 or higher are generally considered high-efficiency.

3. AFUE (Annual Fuel Utilization Efficiency):

The AFUE rating is used to measure the efficiency of furnaces—heaters that burn fuels such as oil or natural gas. As the Department of Energy states, the issue here is how much of the energy from the fuel actually goes toward heating the home, versus being lost as exhaust. Like the SEER and HSPF ratings, AFUE measures the total amount of heat produced for the home over the course of the heating season, divided by the total amount of energy in the fuel used during that time.

Unlike the SEER or HSPF ratings, AFUE is stated as a percentage. Older, low-efficiency systems will often have an AFUE of 70% or lower, meaning 30% or more of the energy in the fuel is being wasted. The current minimum AFUE rating for new furnaces is 81%. However, today’s high-efficiency furnaces have AFUE ratings of 90% or higher.